It is not quite time to plant your onions yet, but it is time to make sure your soil is prepared and that you choose the right onion plant for our growing season.  Onions are best grown in a raised bed at least 4 inches high.  If you do not have raised beds, ensure the soil is loose, well-drained soil of high fertility and plenty of organic matter.  Onions grow best with a pH between 6.2 and 6.8.

There are three types of onions and they are characterized by day length.  Long-day onions, which grow better in the northern states, quit forming tops and begin to form bulbs when the day-length reaches 14-16 hours.  Short-day onions, which grow better in the southern states, will start making bulbs earlier when there are only 10-12 hours of daylight.  Intermediate-day onions, which are great for the mid-state gardens, require 12-13 hours of daylight to form bulbs.  We want to plant intermediate-day onions in our area.  Three varieties that do well here are:

  • Sweet Candy Red(red onion)
  • Super Star Hybrid(white onion)
  • Hybrid Candy(yellow onion)

Once you choose the variety(ties) you like,  order them as plants through a catalog or your local nursery.  Onions plants do so much better in our area than sets.  Plant them 1 inch deep and 4 inches apart.  If you like to harvest early green onions, plant some 2 inches apart.

Onions are heavy feeders, so make sure you provide ample amounts fertilizer based on the type of fertilizer you are applying.  After two-three weeks of planting apply a side-dressing of fish emulsion, ammonium sulfate or ammonium nitrate.  Continue to fertilize every 2-3 weeks until the neck feels soft which will be approximately 4 weeks prior to harvest time.  Make sure your onions stay well watered throughout the season.  The ground does not need to be soggy, but don’t let them dry out.

Harvest your onions when the leaves start to fall over and turn brown, this is generally late August.  Onions must be cured prior to storing them.  Allow them to cure for about two weeks in a well ventilated area out of direct sunlight.  For more in depth details on growing, caring for and storing of onions check out: http://www.ext.colostate.edu/ptlk/1808.html

Article written by Rich Young, Colorado Certified Gardener.

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